One of the major environmental problems of today is to preserve potable water supplies from contamination. This is particularly difficult in areas near waste disposal or spill sites where the waste materials often eventually find their way into aquifers or areas of water storage. This will normally come about by the percolation of aqueous or nonaqueous liquid contaminants through permeable soil directly into the acquifer or water supply.
One way to prevent contaminants from entering aquifers or water supplies is to line the bottom of a proposed waste storage site with an impermeable liner prior to use of the site. This requires excavation of the area down to the design depth of the site and the placement of such a liner, which may comprise any suitable barrier such as a flexible plastic liner or a cement base. The labor involved in such an operation, however, can be quite time consuming and expensive. Moreover, this approach does not solve the problem of contamination from existing waste storage sites which were not originally provided with liners. Nor does it solve the problem of preventing the leakage of pollutants from existing storage tanks, for example, gasoline storage tanks used at service stations, from eventually entering our our water supplies.
It has been suggested to erect barriers to the migration of contaminants through the soil by injecting a liquid sealant into the soil to both move the earth and provide a seal against the flow of fluids. In U.S. Pat. No. 4,491,369, for example, a method of upwardly displacing an entire massive earth block for the purpose of sealing the perimeter and lower face of the block is disclosed. Vertical trenches are dug corresponding to the perimeter of the block to be lifted and sealed, and the trenches are then sealed so that the amount of pressure required to lift the block by the injection of a low solids content slurry at the base of the block can be minimized. The horizontal extent of the layer which seals the lower face of the block is thus required to be established by the trench layout. The entire operation of trenching and sealing the vertical and horizontal boundaries of the massive earth block requires a great deal of labor and is too time consuming and costly for many waste disposal sites.
Another approach to isolating and controlling underground liquids is found in U.S. Pat. No. 4,637,462 which discloses the use of a nunmber of injection wells from which an expansive slurry, such as bentonite, is injected into the surrounding formation to seal the area around a length of the well. By following this procedure with a number of injection wells located around the periphery of the site, a peripheral vertical boundary to the flow of fluids into and out of the area is created. To isolate the bottom of the site, the use of separate slant injection wells is suggested.
The use of injected material to form vertical seals at the periphery of a zone and at the bottom of the zone is also suggested in U.S. Pat. No. 4,645,382, using injection methods which are described in the patent as being established techniques.
Since the prior art methods of isolating waste material from ground water supplies appear to be either highly specialized or too costly and time consuming to be used in connection with many waste disposal sites, it is a main object of the invention to provide a swift, inexpensive method for isolating a contamination site at any relative shallow predetermined depth without having to embark on an involved, expensive operation, and to be able to do so in a relatively short period of time.